The two then traded expletives, and Mr. Weeks asked Mr. Bulger: “What do you want to do?”

U.S. marshals were forced to stand between the two, until the judge dismissed Mr. Weeks.

Mr. Bulger faces charges related to the deaths of 19 people. He’s accused of heading up Boston’s Irish mob for nearly two decades, and he also faces allegations of extortion, racketeering and money laundering.